Bills wife goes out to buy a car. The salesman says, I recommend this one.
She asks why. The salesman says, Because it has hydraulic backspin brakes. Get in and Ill show you.

He drives the car 100 miles and hour toward a brick wall, and when he's 100 feet away he jams on the brakes. They stop a foot from the wall.

The salesman says, Do you smell that? She takes a sniff and says, Uh-huh. The salesman says proudly, That's hydraulic backspin brakes.

That night when Bill gets home, his wife says, Dear, I bought a car.
Bill asks, How did you decide which kind to buy? She says, I bought one with hydraulic backspin brakes. Get in and Ill show you.

They get in, and she drives 100 miles an hour toward the same brick wall. When they are 100 feet away from it she jams on the brakes, and they stop one foot from the wall.
She looks over at her husband and says. Do you smell that?